Oil/fuel Mixture for older motors

I am a bit new to the world of outboards. I am curious as to what the school of thought is on the fuelil mixture ratio for old engines. I know that some older engines require a ratio as high as 16:1. Does this still apply or can the ratio be lowered by using TC-W3 oil? I have read postings on other sites that say that if you mix 16:1 you should not use TC-W3, but a regular 2-cycle oil instead. I was wondering if 16:1 was a standard before TC-W3 was developed and if standards have changed since. I'm a bit confused.

Re: Oil/fuel Mixture for older motors

Hi Full Boat,<br /> In general, the oil ratio you should use is the one as recommended by the manufacturer. There are exceptions to this, but for the most part you won't hurt your motor by following that recommendation. The exceptions of note are cases where the original recommendation was TOO lean, .ie late 1980s OMC kickers that were 100:1 are now 50:1, as per factory service bulletin.<br /> Take a look at my general recommendations on the FAQ section. It isn't meant to be the last word on oil ratios, but should get you going without danger of cooking your motor. <br /> Stick to the best oil you can afford for your motor, with a minimum of TC-W3 rating. Older or lesser rated oils are just that - older and inferior... Also, original recommendations for many very old motors were to use SAE 30 wt. oil. That is one original recomendation that has gone by the wayside due to their not even being "2-stroke" oil back in the day. Modern 2-stoke oils are far better at lubrication, mixing with the gas, cleaner burning, etc. than 30 wt. was ever meant tobe.<br /> Hope that helps,<br />- Scott

Re: Oil/fuel Mixture for older motors

In general, Fullboat, all modern, water cooled 2 strokes use a 50:1 ratio of TC-W3 and regular unleaded.<br /><br />In 1964, OMC specified that all OMC engines made before that date should/could use a 24:1 ratio with TC-W_ oil, and all after that date should use a 50:1 ratio..<br /><br />Many air cooled engines require richer ratios, and all should use oil formulated for air cooled engines. I have seen weedwhackers and chainsaws that call for 40:1, but I have also used air cooled engines that needed as rich as 8:1.<br /><br />Generally, the Clinton and Tecumseh air cooled powerheads on outboards use a 16:1 or 24:1 ratio with chainsaw oil.<br /><br />It is always best to use maker's recommendations on engines less than 40 years old, and update recommendations on older engines to use TC-W3 and unleaded gas.<br /><br />Good luck, and welcome to iboats.

Re: Oil/fuel Mixture for older motors

Originally posted by JB: <br />It is always best to use maker's recommendations on engines less than 40 years old,

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And I think that if the previous owners did, thats WHY its still running 40 year's later!

Re: Oil/fuel Mixture for older motors

Your 4Hp Merc twin should be okay at 50:1.